Process and apparatus for manufacturing isotropic nonwovens

ABSTRACT

The invention relates to a process and an apparatus for manufacturing of a nonwoven. In order to be able to cost-effectively produce a nonwoven, which is to a great extent isotropic in machine and cross direction, a double-layer web is produced according to the invention by one single web forming device, where the one partial web consists of mainly lengthwise oriented fibers and the other partial web laid in zigzag—the cross-fiber partial web—consists of mainly crosswise oriented fibers. The primary fleece for the cross-fiber partial web is taken off the web forming process at a several times higher speed than the fleece of the other, slower partial web. Both partial webs are redirected and oriented to each other in such a way, that they can be brought together to form a double-layer complete web. This double-layer web produced in a cost-effective way is then bonded to form a nonwoven which is to a great extent isotropic.

FIELD OF THE INVENTION

[0001] The invention relates to a process for manufacturing of anonwoven, which shows almost the same tensile strength and elongationproperties in longitudinal direction (machine direction, MD) and crossdirection (CD) (a so-called isotropic non-woven), as well as to acorresponding production line.

DESCRIPTION OF THE PRIOR ART

[0002] It is generally known that, due to the fact that in the webformation process and in particular in the common carding process fibersmainly orient themselves in longitudinal direction, nonwovens show ahigher strength and a lower elasticity in the laid longitudinal fiberdirection in comparison to the corresponding values in the directionwhich is at right angles to the preferred fiber orientation. Thisdifference in CD/MD strength can be observed in all nonwovensindependent of their type of bonding, i.e. this difference not onlyoccurs with thermally bonded but also with mechanically bonded nonwovense.g. needle-punched webs or even stitch-bonded nonwovens, whereas in thelatter, the fibers are at least stitch-bonded on one side of thenonwoven.

[0003] Attempts have already been made to counteract a longitudinalorientation of the fibers during the web formation process, but afterall with only little effect. The reorientation of the fibers in crossdirection, which can be achieved during the web formation process, isonly modest with regard to the angle and/or the portion of the fibersoriented crosswise in relation to the total mass of fibers. Frequently,crimped fibers are used or the fibers are compressed when the web istaken off from the card, which increases the elasticity in machinedirection but only results in a slight increase of the CD strength.

[0004] Different proposals relate to the possibility of eliminating orat least decreasing the stated anisotropy of the web, which results fromthe production process, later in the bonding process. In connection withstitch-bonded nonwovens, some of these proposals relate to a specialstitch bonding technique, which shall result in a higher CD strength(cf. the patent specifications oft the former DDR [German DemocraticRepublic] DD 283,169 A5; DD 283,171 A5; DD 288,634 A5). Another approachof improving the CD strength is to insert cross threads during thebonding process, in particular during the stitch-bonding process, and tointegrate these cross threads in the nonwoven (cf. DD 285,383 A5). Butby means of the processes mentioned here, the CD strength of a nonwovencan only be improved to an insufficient degree.

[0005] In the field of nonwoven production, in particular ofneedle-punched webs, it is a custom to transform a web with moderatewidth coming from a card by laying it in a zigzag in cross direction toform a new web length with a higher width and a higher fiber mass persurface unit, and to mechanically bond this new web length for exampleby needling (cf. for example the German book publication“Vliesstoffe—Rohstoffe, Herstellung, Anwendung, Eigenschaften, Prüfung”,edited by W. Albrecht, H. Fuchs, W. Kittelmann, Wiley-VCH, Weinheim,2000, ISBN 3-527-29535-6, page 158, “Aufgaben des Vlieslegers”; thisbook is cited several times hereinafter with different chapters). Withinthe web length formed by laying a fleece in zig-zag, the main part ofthe fibers is oriented at right angles to the running direction of thisweb length. As a result, the CD strength is higher than the MD strength,so in principle, the difference persists, although just the other wayround.

[0006] Therefore, one has proceeded to draft these cross-laid zigzagwebs before entering the needling process, so that the fibers arebrought from a cross orientation into an orientation which is at anangle to the edge of the web (under a preferred angle α). Namely, when aweb is drafted the fibers of which are oriented crosswise, about half ofthe fibers orient themselves at an angle +α and the other half of thefibers at an angle −α. Thus, the fibers in the web cross themselves (cf.the above mentioned book publication “Vliesstoffe”, page 165 f about webdrafting). Such a drafting process can provide for an approximation ofthe strength values in machine and in cross direction and serve toeliminate the anisotropy for the most part. Besides, this type of webformation in principle also allows for other bonding processes besidesneedling. The disadvantage, however, is that the directions which showthe highest strength are not those directions which are lying inparallel or at right angles to the side edges of the web length, butlying under the said angle ±α. To be able to use the strength of the weblength in an optimal way, for fabrication the parts would have to be cutout of the web length at an angle (the angle α). For financial reasons,this method only used in exceptional cases because of the resultingtriangular waste parts which cannot be used.

[0007] Another proposal which also relates to the field of stitchbonding technology (cf. German Offenlegungsschrift DE 198 43 078 A1) forthe formation of an almost isotropic bulky stitch-bonded nonwoven with ahigh portion of standing fibers consists of preparing a thicker web ofany width by laying a uniform fiber fleece in zigzag the fibers of whichare mainly oriented lengthwise. As the fibers of this thicker web areoriented at right angles to its longitudinal direction, the web shows ahigher strength in the cross direction. The subsequent treatment of thisweb is effected at right angles to the working direction of the webforming machine of the primary fleece and at right angles to theorientation of the fibers. By mechanically bonding this web using thestitch bonding technique on at least either the top or the bottom side,the MD strength is increased, because in the stitch bonding process manyfibers are reoriented into the working direction of the stitch bondingprocess. Thus, the stitch bonding technique can provide for animprovement of the poor MD strength of the web laid in zigzag and for areduction of the inequality. By this procedure, however, a completebalance of MD/CD strength can only be achieved to a limited degree. Thisis because the approximation of the strength properties in machine andcross direction depends on the fiber mass of the web per surface unitand on the portion of the fibers which can be oriented lengthwise byusing the stitch bonding technique, i.e. the degree of stitch bonding.By the way, this web formation process is bound to the mechanicalbonding of the web by means of the stitch-bonding technique.

[0008] Another proposal also relating to the field of stitch-bondednonwovens according to the patent specification of the former DDR(German Democratic Republic) with the number DD 292,489 A5 uses severalfiber layers in the web with fibers of different orientations, which arelying in parallel and/or crosswise to the edge of the web length and arecrossing each other. In the process presented in said publication, thefiber web is composed of two separate layers, one of which consists ofmainly lengthwise oriented fibers and the other consists of mainlycrosswise oriented fibers. In this process, the individual fiber layersare first produced by separate web forming devices and after bringingtogether the two layers, the common web is subject to a mechanical webbonding process using the stitch bonding technique. With thesedouble-layer webs, isotropic stitch-bonded nonwovens with a high portionof standing fibers can be produced. The disadvantage of this process is,however, that two separate web forming devices are needed. Because ofthe considerable investment costs which are necessary, the productioncosts per surface unit for the final product are extremely high, so thatthe produced stitch-bonded nonwovens perhaps can be no longer offered onthe market at a competitive price.

[0009] It is known that for the formation of nonwovens several fleecesare united to form one web in order to homogenize the local density overthe surface of a nonwoven with the aid of at least one web formingdevice with two web doffing devices or several web forming devicesplaced in line one after the other (cf. the said book publication“Vliesstoffe”, page 157 f about web formation). Here, in at least oneweb forming process or in several web forming processes taking placesimultaneously, the same raw fibers and/or the same blend of raw fibersare used to produce at least two separate fleeces of the same width,which are guided over different ways and afterwards are guided at thesame speed and in the same direction as well as with the samepositioning in cross direction to be reunited to a common web. Becauseof the layer structure of the web resulting from the use of severalfleeces, any local differences in density are compensated for to a greatextent. Afterwards, the web produced in such a way is bonded to form anonwoven by using any bonding method. But with this technique, the MD/CDstrength ratio cannot be influenced to a considerable degree.

SUMMARY OF THE INVENTION

[0010] It is an object of the invention to present a process and adevice for the formation of a nonwoven which is to a great extentisotropic in machine and in cross direction, the maximum strength valuesare achieved in parallel and/or at right angles to the lateral edge ofthe web length. Another object of the invention consists therein thatsuch a nonwoven can be produced at low investment cost and which can bebonded using any bonding process.

[0011] According to the invention these objects are achieved therebythat a double-layer web is produced on a single web forming device, onelayer of fibers is composed of mainly lengthwise oriented fibers and theother fiber layer laid in zigzag contains mainly crosswise orientedfibers. The fiber layer laid in zigzag is redirected and broughttogether with the other fiber layer. This double-layer web, which is toa great extent isotropic and which has been produced at low cost, canafterwards be bonded by any bonding technique to form a nonwoven.

[0012] Other objects, advantages and novel features of the presentinvention will become apparent from the following detailed descriptionof the invention when considered in conjunction in with the accompanyingdrawings.

BRIEF DESCRIPTION OF THE DRAWINGS

[0013]FIG. 1 shows a perspective drawing of a double-layer web for theformation of a nonwoven, which is composed of a lower web layer withlengthwise oriented fibers and of an upper partial web with crosswiseoriented fibers,

[0014]FIG. 2 is a perspective drawing of a three-layer web with a mediumpartial web with crosswise oriented fibers and an upper and a lower weblayer with lengthwise oriented fibers,

[0015]FIG. 3 shows a first embodiment of a device for the formation of amultilayer isotropic nonwoven. Here, the working direction of the webformation device and the device for bonding the nonwoven are in truealignment, but in the course of the faster or cross-fiber partial web adouble redirection by 90° compensating itself takes place, i.e. first amere redirection of the faster partial web to the cross direction andthen a redirection by 90° immanent to the process by laying in zig-zagthe faster partial web to form the cross-fiber partial web,

[0016]FIG. 4 contains a second embodiment of a device for the formationof a multilayer isotropic web where the working direction for the webformation and for the subsequent treatment of the complete web also arein alignment. In the course of the faster or cross-fiber partial web,also a double redirection by 90° compensating itself takes place, but inthis case, the faster partial web is laid in zigzag to form thecross-fiber partial web under a first redirection by 900 and afterwardsanother redirection of this web back to its original direction,

[0017]FIG. 5 shows a third embodiment of a device for the formation of amultilayer isotropic web, where the working direction for the webformation on the one hand and the device for the bonding of the web onthe other hand are arranged at right angles to each other and where notonly in the course of the slower partial web but also in the course ofthe cross-fiber partial web a redirection by 90° takes place. For thecross-fiber partial web, this redirection results from laying the web inzigzag and for the slower partial web, the redirection was necessary inorder to guarantee that the web runs in the same direction and has thesame position in cross direction,

[0018]FIG. 6 is a separate perspective drawing of a spacesaving webredirecting device.

DETAILED DESCRIPTION OF THE DRAWINGS

[0019] The subject matter of the invention to be discussed on the basisof different embodiments is a device and a process for the formation ofa multilayer isotropic nonwoven, which is mechanically bonded at leaston either the top or the bottom side using any kind of bonding method,but preferably by stitch-bonding the surface-near fibers, and where atleast one layer in the web is composed of cross-oriented fibers. Thenonwoven, which according to the invention can be produced at lowinvestment cost, shall be to a great extent isotropic in machine andcross direction, and the maximal strength values shall be achieved inparallel and/or at right angles to the lateral side of the web length.

[0020] According to the invention, with the process and/or therespective production line a multilayer web produced at low cost shallbe delivered to the subsequent web bonding process. The multilayercomplete web 4 which shall be bonded to form a nonwoven, is composed ofat least one partial web 5 with mainly lengthwise oriented fibers 3′ andanother, cross-fiber partial web 1 which is produced by laying thefleece in zigzag and the fibers of which are mainly oriented crosswise3, as shown in perspective in FIG. 1 for a double-layer web. In thisprocess, it is not essential, whether the cross oriented partial web 1or the lenthwise oriented partial web 5 is situated at the top or at thebottom of the complete web 4. This is more important for the usedbonding method and the subsequent use of the nonwoven. Moreover, bothpartial webs have to a great extent the same surface weight. In aspecific case, the distribution of the fiber quantities among the twopartial webs 1 and 5 will be chosen empirically depending on the usedbonding method and the intended use of the nonwoven.

[0021]FIG. 2 contains a perspective drawing of a three-layer web 6,which at the bottom and at the top is composed of a “straight” partialweb 5′ and/or 5″ with mainly lengthwise oriented fibers 3′, whereas thecross-fiber partial web 1″ placed between these two webs contains mainlycrosswise oriented fibers 3′. For the three-layer structure of the web,it is essential that the cross-fiber partial web 1″ is situated in themiddle.

[0022] The further explanations only relate to the costeffective andrational production of a double-layer web 4. The devices for theformation of such a nonwoven in the different embodiments described inthe FIGS. 3, 4 and 5 generally contain the following components:

[0023] First, a device for the dry web formation has to be provided,which in principle can be of any design, but with the restriction thatonly those web formation devices are taken into consideration whichallow for simultaneous and locally displaced doffing of at least twowebs or fleeces and which also allow for considerable differences inspeed when doffing the webs. With regard to the web formation processes,in particular the above mentioned book publication “VliesstoffeRohstoffe, Herstellung, Anwendung, Eigenschaften, Prüfung”, edited by W.Albrecht, H. Fuchs, W. Kittelmann, Wiley-VCH, Weinheim, 2000, ISBN3-527-29535-6 shall be referred to. In chapter 4 _(“)Trockenverfahren”(page 137 to 228), this textbook deals with the different processes forthe dry web formation and in subchapter 4.1.2 _(“)Faservliese nach demKardierverfahren”, in particular the pages 145 to 157 deal withindividual aspects of the process and machine technology of webformation on cards. To the knowledge of the applicant, only cards orcarding machines provide several doffers, which moreover can be drivenat highly different speeds if the wires on the doffers are equippedaccordingly. For this reason, the embodiment in FIG. 3 outlines a webforming card 10.

[0024] The web forming card 10 is equipped with two doffers 11 and 12staggered in height. Because of the corresponding equipment of itswires, one doffer 11 outlined at the bottom in FIG. 3 is designed insuch a way that it allows for a much higher doffing speed V₂ whendoffing the partial web 2 than the other doffer 12 shown at the top inFIG. 3. At this doffer, the doffing speed is only v₁. The relation v₁/v₂of the two doffing speeds will be dealt with below in more detail. Atthis point it shall only be mentioned that if per unit of time, at thetwo doffers a fiber mass of almost the same size is doffed, the surfaceweight of the fleece doffed at the lower, faster doffer 11 is incompliance with the speed ratio more light-weight than the slower fleece5 doffed at the other doffer 12. But by laying the faster partial web inzigzag to form a slower cross-fiber partial web 1, the surface weight ofthis web is increased again in compliance with the speed ratio v₁/v₂.

[0025] In the sequel of the explanations, the abridged terms _(“)fasterweb doffer 11”, _(“)faster partial web 2”, _(“)slower web doffer 12” and“slower partial web 5” are used.

[0026] As to the fiber mass actually taken off in a real case at the webdoffers 11 and 12 and/or the mass ratio, this is above all dependent onthe bonding method and on the intended use of the nonwoven to beproduced. If the nonwoven is to be stitch-bonded, it is quite useful forthe slower partial web 5 with lengthwise oriented fibers to have aconsiderably smaller share in the fiber mass (e. g. 35 percent inweight) compared to the faster partial web 2 the fibers of which laterwill be oriented crosswise (e. g. 65 percent in weight), because theportion of fibers oriented lengthwise will be increased again by thebonding stitches and/or the stitch wales. In general it can be said,that the web forming device takes a fiber mass of approximately the samesize per unit of time for the faster partial web 2 as for the slowerpartial web 5, whereas this is a rough approximation which allows for adifference of ±20 percent in weight. Thus, the range of massdistribution can extend from about 30:70 to 70:30.

[0027] In all variants of the invention shown in FIGS. 3, 4 and 5, thefaster partial web 2 is assigned at least indirectly a web laying device14, 22 or 45 respectively, which provide for laying the faster partialweb 2 in zigzag to form the cross-fiber partial web 1. The partial webis in each case led to the web laying device by means of transportbelts, which is, however, not shown in the simplified basic type ofdrawing of the FIGS. 3 and 5. In the embodiment in FIG. 4, the transportbelt 21 is shown which serves to feed the faster partial web 2 to theweb laying device 22. By laying the faster partial web 2 in zigzag, across-fiber partial web 1 is produced, which consists of fibers 3 mainlyoriented at right angles to the longitudinal direction of the weblength. By laying the faster partial web 2 in zigzag to form across-fiber web 1, its running speed is decreased and at the same time,its surface weight is increased accordingly. In connection with thelaying of webs in zigzag it must also be referred to the above mentionedtextbook ,_(“)Vliesstoffe”, which in subchapter 4.1.2.3_(“)Vliesbildung” (pages 157-165) deals with the process and machinespecific aspects of the cross-lapping or zigzag laying of fleeces inparticular to form cross-oriented webs. Here it is differentiatedbetween different designs of web laying devices, inter alia steep armlappers (Camelback) and horizontal lappers. To simplify matters, in theembodiments shown in FIGS. 3 and 5, oscillating steep arm lappers areoutlined as web laying device 14 or 45 respectively, and for theembodiment in FIG. 4, a basic drawing of a horizontal lapper is providedas web laying device 22 in the design of a carriage lapper.

[0028] Since the two partial webs that is to say the slower partial web5 and the cross-fiber partial web 1 laid in zigzag shall be united toform one common complete web 4, they do not only have to be of the samewidth but have also to be brought together with the same position incross direction and with the corresponding speed of the web length. Inorder to be able to fulfil this dimensional condition, in generalcertain process conditions apply to the web laying devices used toguarantee that the above mentioned geometric conditions can befulfilled, i.e. the same width and the same speed of the cross-fiberpartial web 1 and the slower partial web 5.

[0029] Namely, the partial layers to be laid in zigzag to form across-fiber partial web 1 have to be laid under such an angle α, thesine value of which corresponds to the value of a proper fraction in theform 1/n where n is an integer less than seven. In other words, thepartial layers to be laid in zigzag to form the cross-fiber partial web1 have to be laid alternatively under one of the angles α mentioned inthe following:

[0030] 30,0° (sin α=½)

[0031] about 19,5° (sin α=⅓)

[0032] about 14,5° (sin α=¼) or

[0033] about 11,5° (sin α=⅕)

[0034] For this purpose, the faster partial web 2 has to be taken offfrom the web forming device with a speed v₂ which is by a correspondingintegral multiple higher than the doffing speed v₁ of the slower partialweb. Thus, the above mentioned ratio of the doffing speeds or thereciprocal v₂/v₁ respectively is preferably two, three, four or five.Despite their possibly varying absolute speed, the two doffers 11 and 12running at different speeds have to run at a fix, adjustable speed ratiocorresponding to one of the stated values. The higher the speed ratiov₂/v₁, the lower the possible angle α between the partial layers laid inzigzag within the cross-fiber partial web 1 and the more likely thefibers 3 of the original fleece are really oriented crosswise within thecross-fiber partial web 1. On the other hand, a speed ratio v₂/v₁ of theweb doffers which is too high not only causes problems when doffing theweb but also when laying the cross-fiber partial web 1 in zigzag. Atechnically feasible upper limit seems to be reached at a speed ratiov₂/v₁ in the order of about 5 to 7. A further increase would only leadto more technical and operational problems and would, from the point ofview of textile technology, not offer more advantages for the finishednonwoven.

[0035] By laying in zigzag the faster partial web 2 by means of a weblaying device 14, 22 or 45 respectively (FIGS. 3, 4 or 5) to form thecross-fiber partial web 1, a process-immanent redirection of the runningdirection of the web length by 90° takes place. On the other hand, thecross-fiber partial web 1 formed in this way and the slower partial web5 shall be brought together with the same direction, the same positionin cross direction and at the same speed. For this reason, the differentembodiments of the production device provides for another webredirecting device 17, 28 or 43 respectively, which provides for thisparallel run of the partial webs to be brought together. This aspectwill be dealt with in detail below when describing the individualembodiments. At this point, it shall only be mentioned that the webredirecting device 17, 28 or 43 respectively of the differentembodiments each are situated differently within the production deviceand/or are assigned to different partial webs. It is in this respect andin the resulting consequences, the embodiments in the FIGS. 3, 4 and 5differ from each other.

[0036] A component of the device and the process, which is essential tothe invention, is the web redirecting device 17, 28 or 43 respectively,which is provided by all individual embodiments, even if with adifferent assignment. All embodiments have in common, that the webredirecting device 17, 28 or 43 respectively, independent of the fact towhich of the partial webs it is assigned, in each case redirects theassigned partial web at right angles as to its running direction shownin the outline. Moreover, all embodiments have in common that the webredirecting device with regard to its part effecting the redirection,i.e. the web redirecting rod 18, 30 or 43 respectively —seen fromabove—is situated approximately at the same position as the effectivepart of the respective web laying device 14, 22 or 45 for the fasterpartial web and is staggered in height with regard to it.

[0037] In connection with the said same positioning of these two Systemcomponents and the respective orientation values on the one hand it hasto be said, that the laying rolls (number 25 in FIG. 4) of the weblaying devices 14, 22, 45 describe a square when travelling back andforward. On the other hand, the web redirecting rod 18, 30 or 43 of theweb redirecting devices 17, 28, 43 each are situated diagonally in asquare of the same size. These two squares, the one of the web layingdevice on the one hand and the one of the web redirecting device on theother hand have to be—seen from above—at the same position.

[0038] After the slower partial web 5 and the cross-fiber partial web 1have been brought together to form the complete web 4, the productiondevice finally integrates a device 13 for bonding the complete web 4 toform a nonwoven, which is only shown in generalized form in FIG. 3.Here, in principle the complete range of known web bonding processes ispossible. In this connection, the reader is referred again to the abovementioned textbook _(“)Vliesstoffe”, which deals in chapter 6_(“)Vliesverfestigung” (pages 269-399) with the known processes of webbonding and in particular with the stitch bonding of webs. In thefollowing, bonding of the multilayer web to form a nonwoven is not dealtwith in more detail, it shall only be mentioned, that a stitch bondingprocess where the stitch wales are oriented in longitudinal direction ofthe web length is the most advantageous both from the point of view oftextile technology and with regard to the intended use of the nonwoven.

[0039] After having dealt so far with the correspondences of thedifferent embodiments in the FIGS. 3, 4 and 5, now the individualembodiments themselves shall be explained in more detail which—asmentioned above—differ mainly from each other by the type of assignmentof the web redirecting device essential to the invention. In case of theproduction device shown in FIG. 3, the web redirecting device 17,represented in a simplified way only by the web redirecting rod 18, isassigned to the faster partial web and is functionally preceding the weblaying device 14. Before reaching the web laying device 14, which isalso represented in a very simplified way and is shown as an oscillatingsteep arm lapper, the faster partial web 2 is _(“)temporarily” broughtinto a direction at right angles to the working direction 7, from whereit is laid to form the cross-fiber partial web 1, by which—in aprocess-immanent way—another redirection by 90° is effected. In thisprocess, the faster partial web 2 or the cross-fiber partial web 1respectively is redirected two times—seen from above—during its course,whereas these two redirections compensate each other after all. Seenfrom above, the running direction of the united complete web 4corresponds to the working direction 7 of the web forming card 10; bothdirections 7 and 8 have the same alignment. By means of a web transportbelt 15, the slower partial web 5 is transported over the webredirecting device 17 and the web laying device 14 situated below. Theprocess of laying the slower partial web with the same position in crossdirection and at the same speed V₁ on top of the cross-fiber partial web1 which is carried by the web transport belt 16 is effected at aposition, which is displaced in working direction from the web layingdevice; a pair of pressing rolls 19 compresses the partial webs beforethey are transported by means of the web transport belt 16 to the webbonding device 13.

[0040] In FIG. 4, only a central part of the production device is shown,i.e. the web formation itself and the doffing of the two partial webs 2and 5 with different speeds v₁ and v₂ on the one hand and the device forbonding the complete web 4 to form a nonwoven on the other hand areomitted in the representation of FIG. 4. The slower partial web 5 iscarried by the web transport belt 20 straight through the productiondevice, i.e. this device is also straight, which means that the workingdirection 7 of the web forming device and the direction of thesubsequent treatment correspond to one another.

[0041] Also like in the embodiment according to FIG. 3, in the deviceaccording to FIG. 4 the web redirecting device 28 is assigned to thecourse of the faster partial web 2 or the cross-fiber partial web 1respectively. But in contrast to FIG. 3, in the embodiment according toFIG. 4, the web redirecting device 28 is assigned to the cross-fiberpartial web 1 and is functionally succeeding the web laying device. Asfor the rest, FIG. 4 shows the complete web redirecting device 28, evenif restricted to those parts essential to the functioning; this will bedealt with below in more detail. Also the web laying device 22, designedas flat building horizontal lapper in the type of a carriage lapper, isshown more detailed in FIG. 4, even if only the elements essential tothe functioning are represented. The faster partial web 2 is transportedby means of a web transport belt 21 to the web laying device 22, whereit is laid on a pair of intermediate transport belts staggered in heightand vertically distant, i.e. not touching each other, a top carriage(belt 24) and a laying carriage (belt 24′) with laying rolls 25, whichmove synchronously but in reverse motion in horizontal direction in therhythm of the zigzag laying. In this process, the faster partial web 2(speed v₂) is laid in zigzag and with a width of the web lengthcorresponding to the original width onto the transport belt 23 which istravelling at the slower speed v₁ and is situated at right angles to thetransport belt 21 and the intermediate belts 24, 24′.

[0042] By laying the fleece in zigzag to form the cross-fiber partialweb 1, a redirection by 900 of the partial web immanent to the processtakes place. By means of the web redirecting device 28 which succeedsthe web laying device 22, this redirection can be compensated by anotherredirection by 90°, and the original direction ⅞ can be adopted again.The web redirecting device 28 is situated above the web transport belt20 for the slower partial web 5 and is arranged with its part that isessential for the redirection of the cross-fiber partial web, i.e. theweb redirecting rod 30, at the same position (seen from above) as theweb laying device 22, which, however, gets not quite clear from theperspective drawing in FIG. 4.

[0043] In order to bridge the height difference of the levels ofdelivery of the web laying device 22 on the one hand and the webredirecting device 28 on the other hand, the web transport belt 23integrates a lifting section 26: By means of clever arrangement ofredirecting and guiding rolls, the belt run of the web transport belt 23is bent in L-shape and is led over to the steeply upward pointinglifting section. The section of the web transport belt 23 effecting thetransport, which carries the cross-fiber partial web leads over to thelifting section 26. To guarantee a secure transport of the cross-fiberpartial web on this steep section, a supporting belt 27 guided inL-shape is provided which in the area of the lifting section 26 clingswith a steeply guided part to the transporting section of the webtransport belt 23. Thus, in the lifting section the cross fiber partialweb is held between web transport belt 23 and the touching supportingbelt 27 while being transported to the top. The upper leg of the L-shapesupporting belt 27 is almost horizontally and is arranged above the webredirecting device 28. The transporting section of the web transportbelt 23 of the lifting section 26 slightly extends into this almosthorizontal leg of the supporting belt 27, so that the cross-fiberpartial web which is transported to the top can be laid there. Thecross-fiber partial web is then transported from the horizontal leg ofthe supporting belt to the guiding belt 32 of the web redirecting device28.

[0044] The web redirecting device 28 shown in detail in FIG. 4 consistsmainly of a driven endless guiding belt 32, which is guided in arectangle via not rotating turning rods 29, 30. Neighbouring sections ofthe guiding belt which follow each other at each a turning rod, enclosewith their lateral sides seen from above—an at least approximate rightangle, whereas the respective top and bottom sides of the guiding beltare on the whole arranged in parallel to each another. At a constantbelt run, such a guidance of a belt is only possible, if a slidingredirection takes place at the turning rods. Thus, the turning rods maynot rotate. For practical reasons, the turning rods are pipes having asmooth and hardened surface.

[0045] The guiding belt 32 of the web redirecting device 28 is drivenwith the speed of the assigned partial web, which in the embodimentshown in FIG. 4 is effected by several pairs of drive shafts 31, onesituated on this side of the guiding belt and the other on the otherside of the guiding belt. In the embodiment according to FIG. 4, therequired running speed of the guiding belt 32 is the—lower—speed v₁ ofthe cross-fiber partial web 1. At this point it shall already bementioned, that also in the example according to FIG. 5, where the webredirecting device 43 is assigned to the slower partial web, the webredirecting device is driven at the lower speed v₁ of this partial web.Only in the embodiment according to FIG. 3, the web redirecting device17 is assigned to the faster partial web 2 and thus has to be driven atthe higher speed v₂ of this partial web, which could possibly prove tobe a certain disadvantage if no anti-friction devices are provided atthe turning rods.

[0046] In the area enclosed by the guiding belt, the turning rods 29, 30can be equipped with several grid-like distributed anti-frictiondevices. These can be balls embedded in the outside of the turning rods,which are freely movable but are securely held, allowing for the guidingbelt to roll over. Another possibility to decrease friction is to buildup an overall air cushion in the contact area between the turning rod29, 30 and the guiding belt 32. In this case, grid-like distributed airdischarge openings have to be provided in the area enclosed by theguiding belt, which are permanently supplied in excess with compressedair from the inside of the pipe-shaped turning rods. In this way, theguiding belt floats so to speak on a compressed air film which at thesame time takes any frictional heat. Moreover, the risk of electrostaticcharge of the guiding belt would be lower, in particular if thecompressed air would be well moistened. Thanks to the compressed airfilm, it would be able to guide the guiding belt 32 over the turningrods without resistance, but this would require a certain power for thegeneration of compressed air which, however, could easily be accepted.

[0047] Of the four turning rods 29, 30, which are necessary to guide theguiding belt 32 in a rectangle and which are situated at the “corners”of the rectangle, one turning rod labelled in FIG. 4 with the number 30plays a special role. Only the two sections of the guiding belt 32coming together at the one turning rod (hereinafter called webredirecting rod 30) actually touch the cross-fiber partial web to beredirected. This web redirecting rod 30 is the only one to redirect thecross-fiber partial web 1. The other three turning rods only serve toguide the guiding belt in a closed rectangle. Moreover, the special webredirecting rod 30 is—seen from above—situated at approximately the sameposition as web laying device 22 and is arranged above it.

[0048] In addition to the redirection of the partial web, the webredirecting device essential to the invention has at least in theembodiment according to FIG. 4 also the task to bring about an exactcorrespondence of the two partial webs to be united with regard to theirwidths. For this purpose, at least one of the turning rods 29, 30, whichguide the endless guiding belt, which are not rotating and which aresituated in parallel to the plane of the adjacent sections of the belt,is pivoted to act as a belt run correction and is equipped with acorresponding swivel drive. Because of the web redirecting rod 30 beingdirectly situated at the point where the two partial webs 1 and 5 cometogether, it would be best suited to effect the correction of the beltrun in so far as it would enable a positioning of the belt in crossdirection by means of an automatic control system with the lowest timedelay between the intervention of the automatic control system and thenew position of the belt run. Possibly, it is practical to also pivotthe turning rod diagonally opposing the web redirecting rod 30 in thesame way and to equip it with a swivel drive. A synchronous but oppositeswivelling of the two pivoted rods would result in a regular belttension over the whole width of the guiding belt despite theintervention of the automatic control system. Besides, this would resultin an overall more stable belt run, i.e. the risk of the belt runcontrol getting unstable due to the intervention of the automaticcontrol system is decreasing.

[0049] In order to be able to properly operate the guiding belt of theweb redirecting device with regard to a positioning of the belt in crossdirection by means of an automatic control system, the guiding belt hasalways to be held under a certain belt tension regardless of thermal orage-dependent extensions or shrinkages. For this purpose, twoneighbouring turning rods of the web redirecting device 28 situated inparallel to the plane of the adjacent sections of the guiding belt runon bearings to be moveable and are equipped with the respective shiftingdrive for tensioning the guiding belt 32. For practical purposes, thetwo turning rods movable to this effect can be moved in parallel to thetwo opposing sides of the rectangle built by the two turning rods. Withthe movability realized in such a way, no angle changes are causedwithin the rectangle when tensioning and thus there is no effect on theposition of the belt in cross direction.

[0050] For the sake of completeness, a variant has to be mentioned inconnection with the embodiment shown in FIG. 4, where—similar to theembodiments according to FIGS. 3 and 5 the cross-fiber partial web 1 islocated at the bottom and the slower partial web 5 is located at the topof the complete web formed by the two partial webs 1 and 5. For thispurpose, on the one hand the web transport belt 20, which carries theslower partial web 5, would have to be guided over the web redirectingdevice 28 and would have to be led to a uniting point on a separate webtransport belt situated at the back of the line. On the other hand, justthis separate web transport belt, which is oriented according to thedirection 8 of subsequent treatment would have to be installed, on whichthe cross-fiber partial web 1 redirected to the direction of subsequenttreatment can be laid by the web redirecting device 28.

[0051] The top side arrangement of the slower partial web the fibers ofwhich are oriented in longitudinal direction offers structural andoperational advantages for the subsequent stitch bonding of the completeweb to form a nonwoven using certain stitch bonding processes.

[0052] In the third embodiment of a production device shown in parts andagain very simplified in FIG. 5, the web redirecting device onlyrepresented by its web redirecting rod 43 is assigned to the slower web.Instead of the web redirecting rod 43 one has to imagine a webredirecting device according to the example in FIG. 4 or according tothe example in FIG. 6. The slower partial web 5 redirected at the webredirecting rod 43 is laid onto the web transport belt 44, which carriesit further in direction 8. Also the cross-fiber partial web 1 isredirected immanent to the process to the direction 8 of the subsequenttreatment which is at right angles to the working direction 7 of the webforming device by laying the faster partial web 2 in zigzag to form thecross-fiber partial web 1. The web laying device 45 lays the zigzagpartial layers of the cross-fiber partial web 1 onto the lower webtransport belt 46, which also travels in parallel to the direction 8 ofsubsequent treatment. Also in this case, the web redirecting rod 43 andthe web laying device 45 are again arranged staggered in height to oneanother but—seen from above—at the same position. The lower partial web5 transported on an inclining section by the upper web transport belt 44is united with the cross-fiber partial web 1 laid onto the lower webtransport belt 46 to form a double-layer complete web 4 whichsubsequently can be bonded to form a nonwoven. In the embodimentaccording to FIG. 5, the web transport belt 44 can also be used toprovide for the slower partial web 5 and the cross-fiber partial web 1having the same position in cross direction, when the corresponding webedge detectors and controllable belt guiding rolls are integrated intothe course of the belt.

[0053] The production device outlined in FIG. 5 is all in all arrangedat an angle—in contrast to the straight devices according to FIGS. 3 and4; the working direction 7 of the web forming card together with thedirection 8 of subsequent treatment enclose a right angle.

[0054] The web redirecting device 28 shown in FIG. 4, which has also tobe included in the calculations of the devices according to FIGS. 3 or5, takes up relatively much space. One can assume, that the rectanglebuilt by the guiding belt 32 which is almost square has a side length ofabout two and a half times the working width of the web forming card.Therefore, it is practical to design the web redirecting device inelevated position so that it can be suspended from the ceilingconstruction of the shop or from a supporting structure located abovethe production line without taking up valuable space at the shop floor.

[0055] In order to decrease the space requirement of the web redirectingdevice, in the embodiment shown in FIG. 6 the guiding belt 51 of the webredirecting device 50 is arranged on two different levels at a distancefrom each other to use a minimum of space. Namely at the section of theguiding belt coming from the web redirecting rod 54 and at the sectionwhich is parallel and opposed in the same horizontal plane, a turningroll 52, 52′ surrounded by 180° by each a section is provided. Thediameter of these redirecting rolls determines the distance of the twolevels of the guiding belt 51. Apart from the low space requirement, theweb redirecting device 50 according to FIG. 6 offers also the advantageof a compact construction. This means, that the supporting structure ofthe individual components such as rolls, turning rods and the like ismore compact and more rigid. Of the four turning rods 54, 55, two at atime lie in the top view at least nearly congruent but staggered inheight by approximately the roll diameter, i.e. they are close together.As in this case two opposing sections of the guiding belt stronglysurround the redirecting rolls 52, 52′, the thing to do would be to useat least one of them to drive the guiding belt 51 of the web redirectingdevice and to equip it with a respective swivel drive. If both turningrolls 52, 52′ are used to drive the guiding belt, it should beconsidered that both turning rolls have to rotate at the same speed butin the opposite direction. For the synchronisation of the two turningrolls to be driven, in this case a reversing gear gearing level betweenthe two turning rolls would be useful. In addition to serve as drive,the turning rolls could also be used to tension the guiding belt. Forthis purpose, they would have to run on bearings to be linearly moveablein the direction of the sections of the guiding belt surrounding themand have to be equipped with the respective shifting drive.

[0056] For the sake of completeness it has to be mentioned, that inconnection with the redirecting device 50 shown in FIG. 6, the guidingbelt 51 of the web redirecting device may also be arranged on twodifferent planes which are inclined to each other instead of beingarranged in parallel planes as shown in the embodiment 50 of FIG. 6 orinstead of being arranged in a common plane as shown in the embodiment28 of FIG. 4. Inclining the two planes to each other would reduce theoverall space needed for the redirecting device too. The sections of theguiding belt 51 coming from the turning roll 52, going around the twoturning rods 55 and running again to the turning roll 52′ are arrangedin FIG. 6 in an upper level. Theses three sections of the guiding belt51 form one half of the whole guiding belt 51 and—in any case—are to bearranged in one plane roughly (there is a small distance between themiddle section at the one hand and the two other sections belonging tothe turning rolls 52, 52′ on the other which can be out of regard inthis respect). There is quite a similar arrangement of sections in alower level going around the turning rods 54 and 55. This latter tripleof belt sections has in any case to be arranged almost in one plane too.But the mentioned two triples of belt sections may be arranged in planesbeing inclined to each other so that the turning rolls 52 and 52′ aresurrounded by the guiding belt only an angle that is less than 180° forinstance by 90° or by 135°.

[0057] For the sake of completeness it has to be mentioned, that inconnection with the three-layer web 6 shown in FIG. 2, a web formingcard with three different doffers or two different web forming cardsconnected in tandem one after the other, which together provide thethree web doffers, would be required. With such a web forming device,three separate partial webs 5′, 2, 5″ are formed in the same web formingprocess with the same raw fibers or raw fiber blend respectively, whichare each taken off at the three different, staggered web doffers. Theweb doffer in the middle is driven by the several times higher speed v₂,whereas the two other web doffers rotate at a lower speed (v₁). At thesetwo doffers, the two slower partial webs 5′, 5″ are taken from the webforming process. The faster partial web 2 taken off at the faster webdoffer is laid in zigzag to form the cross-fiber partial web 1, forwhich a redirection immanent to the process takes place. Afterwards,also in this case the cross-fiber partial web 1 and the slower partialwebs 5′, 5″ are synchronised, for which the embodiments shown in theFIGS. 3, 4 or 5 could serve as an example. Then, the three partial webs5′, 1 and 5″ are joined at the same speed v₁, with the same directionand the same position in cross direction to a three-layer complete web6, which finally can be bonded to form a nonwoven.

What is claimed is:
 1. Process for the formation of a nonwovenconsisting of the following process steps: in the same web formingprocess, two separate partial webs are formed out of the same raw fibersor raw fiber blend respectively on a web forming device with two webdoffers, the partial web—hereinafter called “faster partial web”—takenoff at a web doffer is taken out of the web forming process at a severaltimes higher speed than the other partial web—hereinafter called “slowerpartial web”. the faster partial web is laid in zigzag to form a newpartial web—hereinafter called “cross-fiber partial web”—with a widthcorresponding to the width of the slower partial web and at a runningspeed corresponding to the speed of the slower partial web, where thefibers are mainly oriented at right angles to the longitudinal directionof the cross-fiber partial web the cross-fiber partial web and theslower partial web are synchronised and are brought together at the samespeed, with the same direction and with the same position in crossdirection to form a double-layer web hereinafter called “complete web”,the complete web produced in this way is bonded to form a nonwoven. 2.Process according to claim 1, wherein the faster partial web is firstredirected to a running direction which is at right angles to theworking direction of the web forming device and is only from thisdirection laid in zigzag to form the cross-fiber partial web and therebyis again redirected immanent to the process, so that its runningdirection—seen from above—is in alignment with the working direction ofthe web forming device, that the slower partial web is lead around theweb redirecting device for the faster partial web and the web layingdevice for laying the cross-fiber partial web and that afterwards bothpartial webs are united to a complete web.
 3. Process according to claim1, wherein the faster partial web is directly laid to form thecross-fiber partial web and as a result is redirected immanent to theprocess to a working direction, which is at right angles to the workingdirection of the web forming device and that the cross-fiber partial webafterwards is redirected again from this cross working direction to takea direction parallel to the working direction of the web forming deviceand brought into alignment with the slower partial web.
 4. Processaccording to claim 1, wherein the faster partial web is directly laid toform the cross-fiber partial web and as a result is redirected immanentto the process in a working direction, which is at right angles to theworking direction of the web forming device and that also the slowerpartial web is redirected in this cross working direction and is broughtinto alignment with the cross-fiber partial web.
 5. Process according toclaim 1, wherein the zigzag partial layers within the cross-fiberpartial web are laid under such an angle the sine value of whichcorresponds to the value of a proper fraction in the form 1/n where n isan integer less than seven.
 6. Process according to claim 1, wherein thepartial layers to be laid in zigzag within the cross-fiber partial webare laid under one of the angles a mentioned in the following: 30,0°(sin α=½), about 19,5° (sin α=⅓), about 14,5° (sin α=¼) or about 11,5°(sin α=⅕).
 7. Process according to claim 1, wherein the faster partialweb is taken off from the web forming device with a speed which is by acorresponding integral multiple higher than the slower partial web,namely at one of the following speeds: at double, at threefold, atfourfold, at fivefold speed.
 8. Process according to claim 1, whereinthe web forming device takes in rough approximation—allowing for adifference of ±20 percent in weight—a fiber mass of approximately thesame size per unit of time in case of the faster partial web as in caseof the slower partial web.
 9. Process according to claim 1, wherein thefaster partial web is taken off from the web forming device at a webdoffer situated in a lower position and the slower partial web is takenoff at a web doffer situated in a higher position.
 10. Apparatus formanufacturing of a nonwoven consisting of the following systemcomponents: a web forming card with two web doffers staggered in height,where the one, preferably lower web doffer—hereinafter called “fasterweb doffer”—is designed in such a way that it allows for a several timeshigher doffing speed v₂ when doffing the partial web—hereinafter called“faster partial web”—at this point than the speed of the otherdoffer—hereinafter called “slower doffers”—at which a partialweb—hereinafter called “slower partial web”—can be doffed, a web layingdevice assigned to the faster web doffer and connected to it by means ofweb transport belts to lay the faster partial web in zigzag to form anew partial web hereinafter called “cross-fiber partial web”, with awidth corresponding to the original width of the faster partial web andwith fibers mainly oriented at right angles to the longitudinaldirection of the crossfiber partial web, another device to direct thecross-fiber partial web to the slower partial web at the same speed,with the same direction as well as the same position in cross directionin order to unite these to form a multilayer web hereinafter called“complete web”, finally a device for bonding the complete web to form anonwoven.
 11. Apparatus according to claim 11, wherein the device forthe orientation of the cross-fiber partial web and the slower partialweb to each other in order to unite the partial webs to form thecomplete web contains a web redirecting device—assigned to one of thepartial webs and staggered in height with regard to the web layingdevice—which effects a redirection of the assigned partial web by 90°with regard to its running direction as seen from above, the webredirecting device being arranged with regard to its part effecting theredirection—seen from above—approximately at the same position as theeffecting part of the web laying device for the faster partial web. 12.Apparatus according to claim 11, wherein the web redirecting device isassigned to the faster partial web and is functionally preceding the weblaying device, so that in the course of the faster partial web or thecross-fiber partial web respectively, because of the two redirectionscompensating each other in the end, the running direction of the unitedcomplete web—seen from above—is in alignment with the working directionof the web forming card.
 13. Apparatus according to claim 11, whereinthe web redirecting device is assigned to the cross-fiber partial weband is functionally succeeding the web laying device, so that in thecourse of the faster partial web or the cross-fiber partial webrespectively, because of the two redirections compensating each other inthe end, the running direction of the united complete web—seen fromabove—is in true alignment with the working direction of the web formingcard.
 14. Apparatus according to claim 11, wherein the web redirectingdevice is assigned to the slower partial web, and that not only therunning direction—seen from above—of the slower partial web namely bythe web redirecting device but also the running direction of the fasterpartial web and the resulting cross-fiber partial web namely by the webredirecting device each are redirected by 90°, so that the runningdirection of the completed web formed by the partial webs—as seen fromabove—is arranged at right angles to the working direction of the webforming card.
 15. Apparatus according to claim 11, wherein the webredirecting device staggered in height with regard to the web layingdevice consists mainly of a driven endless guiding belt, which is guidedin a square polygon, preferably in a rectangle via not rotating turningrods, the neighbouring sections of the which follow each other at each aturning rod enclose with regard to the lateral sides of the guidingbelt—seen from above—an at least approximate right angle, whereas therespective top and bottom sides of the guiding belt are arranged mainlyin parallel to each another, and where one of the four turning rodshereinafter called “web redirecting rod” is arranged —seen from above—atalmost the same position to the web laying device and where the partialweb to be redirected is guided by the two sections of the guiding beltcoming together at the web redirecting rod and is redirected with it.16. Apparatus according to claim 11, wherein the guiding belt of the webredirecting device is driven at the speed of the assigned partial web.17. Apparatus according to claim 11, wherein the guiding belt of the webredirecting device is arranged on two different levels having a distancefrom each other to use a minimum of space, by arranging in the sectionof the guiding belt coming from the web redirecting rod and in thesection diametrically opposed, approximately in the middle, each aturning roll surrounded by this section by by 180°.